Wu C I, Maeda N
Nature. 1987;327(6118):169-70. doi: 10.1038/327169a0.
As the mechanisms for replicating the two strands of duplex DNA differ it is, in principle, possible for the mutation rates to differ depending on which strand is being copied. In the absence of selection this would lead to a difference in the measured rate of a particular base substitution, such as T to C, depending on which DNA strand was analysed to determine the rate. Thus a change such as T to C on one DNA strand results from either a direct T-to-C mutation on that strand or an A-to-G mutation on the complementary strand; for the other strand the situation is reversed, and it can be seen that different processes are responsible for the two cases, allowing for asymmetry in substitution rate. We have tested whether such asymmetry indeed occurs by studying equivalent sequences from the beta-globin complexes of six species of primate. Our results reveal an asymmetry in substitution rates consistent with predictions based on strand-inequalities in mutation rates. Our sequence comparisons also allow us to make predictions about the positions of replication origins and the replication error rates of one strand relative to the other.
由于双链DNA两条链的复制机制不同，原则上，突变率可能因复制的是哪条链而有所不同。在没有选择的情况下，这将导致在测量特定碱基替换率（如T到C）时出现差异，具体取决于分析哪条DNA链来确定该速率。因此，一条DNA链上的T到C的变化是由该链上直接的T到C突变或互补链上的A到G突变引起的；对于另一条链，情况则相反，可以看出这两种情况是由不同的过程导致的，从而允许替换率存在不对称性。我们通过研究六种灵长类动物β-珠蛋白复合体的等效序列，测试了这种不对称性是否确实存在。我们的结果揭示了替换率的不对称性，这与基于突变率链不平等的预测一致。我们的序列比较还使我们能够预测复制起点的位置以及一条链相对于另一条链的复制错误率。
